1. Field of the Invention
The present invention generally relates to a light controlling sheet in use for optical indicators such as cathode ray tubes, liquid crystal indication devices and the like, and more particularly to a light controlling sheet for permitting only substantially parallel light to pass therethrough.
2. Description of the Prior Art
Conventionally, there has been provided a light controlling sheet as shown in FIG. 1. The light controlling sheet comprises a louver element 1. A transparent base film 3 is generally cemented with one surface of the louver element 1. The louver element 1 includes a plurality of walls 2 which are arranged parallel to each other on the transparent base film 3 and which may be formed in arbitrary patterns, such as honeycomb, stripe and grid patterns. The louver element 1 is opaque so that the light striking thereto can be absorbed therein. When the above light controlling sheet is applied to an indication device, a light source (not shown) is positioned behind the transparent film 3. The oblique light L.sub.1 emitted from the light source strikes the surface of the walls 2 of the louver element 1 to be absorbed therein. In the meanwhile, the substantially parallel light L.sub.2 can pass through the space between the adjacent walls 2. Thus, only the substantially parallel light can reach the observer
In addition, according to the light controlling sheet, the extraneous light L.sub.0 except that within a predetermined angle of incidence can be excluded. Therefore, the reflection of the extraneous light L.sub.0 at the indication face can be effectively prevented.
In the meanwhile, since the conventional light controlling sheet is generally made of insulating synthetic resin, it has the following disadvantages. That is, if the light controlling sheet is applied to for example, a cathode ray tube, it is charged with static electricity. Further, the conventional light controlling sheet can not shield the unwanted electromagnetic wave.